scholarly journals Damage to the Microstructure and Strength of Altered Granite under Wet–Dry Cycles

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 716 ◽  
Author(s):  
Xuxin Chen ◽  
Ping He ◽  
Zhe Qin
Keyword(s):  
Friction Angle ◽  
Damage Mechanism ◽  
Mechanical Tests ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Altered Granite ◽  
Strength Tests ◽  
Number Of Cycles

This paper presents an analytical method for surrounding rocks in symmetrically shaped tunnels or roadways, with the symmetrical rise and fall of groundwater over a certain period. The influence of reservoir water level on wet–dry cycles were studied. The changes in the microstructure and strength of altered granite and its evolution were explored using mechanical tests and scanning electron microscopy (SEM). The results showed that: (1) the wet–dry cycles weakened the strength of altered granite. Furthermore, the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle decreased with the increase of the number of cycles, while the maximum reduction in these parameters reached 50.22%, 63.84%, 93.76%, and 53.90%, respectively. (2) The wet–dry cycles damaged the microstructure of altered granite. The SEM analysis showed that, under wet–dry cycles, the structure of altered granite changed from a smooth and integrated internal structure to the initiation, development, and expansion of pores and cracks. The porosity and fractal dimension of rock were determined using the SEM results. The degree of damage to altered granite under wet–dry cycles was quantitatively analyzed. (3) According to the rock mechanics strength tests and SEM and X-ray diffraction analyses, the damage mechanism of altered granite subjected to wet–dry cycles was discussed. The results provide the basis for a stability analysis of symmetrically shaped tunnels, especially symmetrical tunnels constructed in water-rich areas such as symmetric circular tunnels and symmetric horseshoe tunnels.

Mechanical Properties of Interface Between Soil-Macadam Aggregate and Concrete Pile

2011 ◽  
Vol 368-373 ◽  
pp. 230-233 ◽  
Author(s):  
Shao Jun Li ◽  
Fan Zhen Meng ◽  
Jing Chen ◽  
Hong Min
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Safety Evaluation ◽  
Friction Angle ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Direct Shear Tests ◽  
Concrete Pile ◽  
Shearing Strength ◽  
Reinforcement Design

The mechanical properties of interface between soil-macadam aggregate and anti-sliding concrete pile are very important for the reinforcement design and safety evaluation of accumulative landslide in the reservoir area of Three Gorges. Soil-macadam aggregate is a complex geomaterial whose properties are totally different with soil or rock. Based on a practical landslide suffering the influence of reservoir water level change and seasonal rainfall, a series of direct shear tests are conducted to investigate the interface mechanical properties between soil-macadam aggregate and concrete pile. Accordingly, the relationship between shear strength parameters and water contents and macadam ratios is presented. The change characteristics of mechanical properties of interface are discussed. The results indicate that shearing strength, inner friction angle and cohesion decrease with less water content. However, as the increment of macadam ratios, the cohesion will decrease gradually, but the shear strength and inner friction angle of interface decrease firstly and then increase after a critical value, the change trend obeys parabolic relation.

scholarly journals Resistance to the alkali-aggregate reaction of sustainable mortars produced with scheelite tailings in replacing natural sand aggregates

2021 ◽  
Vol 10 (14) ◽  
pp. e567101422209
Author(s):  
Brunna Lima de Almeida Victor Medeiros ◽  
Jucielle Veras Fernandes ◽  
Fabiana Pereira da Costa ◽  
Sâmea Valensca Alves Barros ◽  
Alisson Mendes Rodrigues ◽  
...  
Keyword(s):  
Mineralogical Composition ◽  
Mechanical Tests ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Natural Sand ◽  
X Ray ◽  
Expansion Test ◽  
Alkali Aggregate Reaction ◽  
Mass Proportion ◽  
Strength Tests

This work produced coating mortars with scheelite tailings (ST) in total replacement of natural sand aggregate. The chemical and mineralogical composition of the scheelite tailings was determined by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Mortar samples with a mass proportion of 1:2:9 (cement: lime: sand/scheelite tailings) were prepared with and without the scheelite tailings. The mortars were evaluated by mercury intrusion porosimetry and compressive and flexural strength tests. The resistance to the alkali-aggregate reaction was assessed from the bar expansion test and by scanning electron microscopy (SEM) in the crack and pore regions. The results indicate that until the 22nd day, the scheelite tailings were not reactive; however, in 28 days, the expansion was deleterious. SEM images did not detect the presence of amorphous alkaline gel characteristic of the alkali-aggregate reaction. Therefore, although the mortar with scheelite tailings aggregate has shown the deleterious potential to 28 days, mechanical tests indicate that it has the potential to be used as a coating mortar.  

Castor Oil and Microcrystalline Cellulose Based Polymer Composites with High Tensile Strength

2011 ◽  
Vol 399-401 ◽  
pp. 1531-1535 ◽  
Author(s):  
Shi Da Miao ◽  
You Yan Liu ◽  
Ping Wang ◽  
Song Ping Zhang
Keyword(s):  
Tensile Strength ◽  
Polymer Composites ◽  
Microcrystalline Cellulose ◽  
Castor Oil ◽  
Mechanical Tests ◽  
Phenyl Isocyanate ◽  
Sem Analysis ◽  
Cellulose Content ◽  
X Ray Diffraction ◽  
High Cellulose

Castor oil and microcrystalline cellulose were employed as biomass feedstock to produce bio-based polymer composites with increased tensile strength. The polymer composites were prepared by curing castor oil with 4,4'-methylenebis (phenyl isocyanate) (MDI) in the presence of microcrystalline cellulose (MC) or modified MC (MMC). The MMC was prepared by reacting MDI with MC to introduce isocyanate groups to the surface of MC. X-ray diffraction spectra suggested the good retention of the crystalline structure of MC or MMC in the composites. SEM analysis showed the well dispersion of MC or MMC in the composites. All of these factors are critical to reinforcing the composites. Mechanical tests of the composites revealed that the reinforcing effect of MMC was more significant than MC at high cellulose content such that the highest tensile strengths of 4.87 MPa was obtained for the composite containing 43% (wt) of MMC. That is almost 5 times higher than that of neat castor oil-based polyurethane.

scholarly journals The Monitoring-Based Analysis on Deformation-Controlling Factors and Slope Stability of Reservoir Landslide: Hongyanzi Landslide in the Southwest of China

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Bing Han ◽  
Bin Tong ◽  
Jinkai Yan ◽  
Chunrong Yin ◽  
Liang Chen ◽  
...  
Keyword(s):  
Water Level ◽  
Water Pressure ◽  
Monitoring Program ◽  
Significant Risk ◽  
Controlling Factors ◽  
Seepage Water ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Reservoir Area ◽  
Reservoir Landslide

Reservoir landslide is a type of commonly seen geological hazards in reservoir area and could potentially cause significant risk to the routine operation of reservoir and hydropower station. It has been accepted that reservoir landslides are mainly induced by periodic variations of reservoir water level during the impoundment and drawdown process. In this study, to better understand the deformation characters and controlling factors of the reservoir landslide, a multiparameter-based monitoring program was conducted on a reservoir landslide—the Hongyanzi landslide located in Pubugou reservoir area in the southwest of China. The results indicated that significant deformation occurred to the landslide during the drawdown period; otherwise, the landslide remained stable. The major reason of reservoir landslide deformation is the generation of seepage water pressure caused by the rapidly growing water level difference inside and outside of the slope. The influences of precipitation and earthquake on the slope deformation of the Hongyanzi landslide were insignificant.

scholarly journals Application of Neural Network Models and ANFIS for Water Level Forecasting of the Salve Faccha Dam in the Andean Zone in Northern Ecuador

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2011
Author(s):  
Pablo Páliz Larrea ◽  
Xavier Zapata Ríos ◽  
Lenin Campozano Parra
Keyword(s):  
Neural Network ◽  
Water Level ◽  
Clustering Algorithm ◽  
Network Models ◽  
Water Levels ◽  
Subtractive Clustering ◽  
Neural Network Models ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Maximum Delay

Despite the importance of dams for water distribution of various uses, adequate forecasting on a day-to-day scale is still in great need of intensive study worldwide. Machine learning models have had a wide application in water resource studies and have shown satisfactory results, including the time series forecasting of water levels and dam flows. In this study, neural network models (NN) and adaptive neuro-fuzzy inference systems (ANFIS) models were generated to forecast the water level of the Salve Faccha reservoir, which supplies water to Quito, the Capital of Ecuador. For NN, a non-linear input–output net with a maximum delay of 13 days was used with variation in the number of nodes and hidden layers. For ANFIS, after up to four days of delay, the subtractive clustering algorithm was used with a hyperparameter variation from 0.5 to 0.8. The results indicate that precipitation was not influencing input in the prediction of the reservoir water level. The best neural network and ANFIS models showed high performance, with a r > 0.95, a Nash index > 0.95, and a RMSE < 0.1. The best the neural network model was t + 4, and the best ANFIS model was model t + 6.

scholarly journals Characterizing the Development Pattern of a Colluvial Landslide Based on Long-Term Monitoring in the Three Gorges Reservoir

2021 ◽  
Vol 13 (2) ◽  
pp. 224
Author(s):  
Xin Liang ◽  
Lei Gui ◽  
Wei Wang ◽  
Juan Du ◽  
Fei Ma ◽  
...  
Keyword(s):  
Time Variable ◽  
Development Pattern ◽  
Three Gorges ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
The Three Gorges ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Colluvial Landslide

Since the impoundment of the Three Gorges Reservoir (TGR) in June 2003, the fluctuation of the reservoir water level coupled with rainfall has resulted in more than 2500 landslides in this region. Among these instability problems, most colluvial landslides exhibit slow-moving patterns and pose a significant threat to local people and channel navigation. Advanced monitoring techniques are therefore implemented to investigate landslide deformation and provide insights for the subsequent countermeasures. In this study, the development pattern of a large colluvial landslide, locally named the Ganjingzi landslide, is analyzed on the basis of long-term monitoring. To understand the kinematic characteristics of the landslide, an integrated analysis based on real-time and multi-source monitoring, including the global navigation satellite system (GNSS), crackmeters, inclinometers, and piezometers, was conducted. The results indicate that the Ganjingzi landslide exhibits a time-variable response to the reservoir water fluctuation and rainfall. According to the supplement of community-based monitoring, the evolution of the landslide consists of three stages, namely the stable stage before reservoir impoundment, the initial movement stage of retrogressive failure, and the shallow movement stage with stepwise acceleration. The latter two stages are sensitive to the drawdown of reservoir water level and rainfall infiltration, respectively. All of the monitoring approaches used in this study are significant for understanding the time-variable pattern of colluvial landslides and are essential for landslide mechanism analysis and early warning for risk mitigation.

scholarly journals Large-Scale Landslide Displacement Rate Prediction Based on Multi-Factor Support Vector Regression Machine

2021 ◽  
Vol 11 (4) ◽  
pp. 1381
Author(s):  
Xiuzhen Li ◽  
Shengwei Li
Keyword(s):  
Support Vector Regression ◽  
Water Level ◽  
Large Scale ◽  
Displacement Rate ◽  
Support Vector ◽  
Single Factor ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Depth Analysis ◽  
Three Factor

Forecasting the development of large-scale landslides is a contentious and complicated issue. In this study, we put forward the use of multi-factor support vector regression machines (SVRMs) for predicting the displacement rate of a large-scale landslide. The relative relationships between the main monitoring factors were analyzed based on the long-term monitoring data of the landslide and the grey correlation analysis theory. We found that the average correlation between landslide displacement and rainfall is 0.894, and the correlation between landslide displacement and reservoir water level is 0.338. Finally, based on an in-depth analysis of the basic characteristics, influencing factors, and development of landslides, three main factors (i.e., the displacement rate, reservoir water level, and rainfall) were selected to build single-factor, two-factor, and three-factor SVRM models. The key parameters of the models were determined using a grid-search method, and the models showed high accuracies. Moreover, the accuracy of the two-factor SVRM model (displacement rate and rainfall) is the highest with the smallest standard error (RMSE) of 0.00614; it is followed by the three-factor and single-factor SVRM models, the latter of which has the lowest prediction accuracy, with the largest RMSE of 0.01644.

scholarly journals A Practical Nonprobabilistic Reliability Assessment Method on Key Strata Shear Failure in Longwall Mining

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hebing Luan ◽  
Jiachen Wang ◽  
Guowei Ma ◽  
Ke Zhang
Keyword(s):  
Structural Reliability ◽  
Shear Failure ◽  
Longwall Mining ◽  
Reliability Assessment ◽  
Friction Angle ◽  
Assessment Method ◽  
Mechanical Tests ◽  
Potential Hazard ◽  
Support Design ◽  
Key Strata

Roof cutting has long been a potential hazard factor in longwall panels in some diggings in China. Meanwhile, the key strata structural reliability, which provides an assessment on the stability of overlying roof strata, may be a significant reference for support design in underground coal mines. This paper aims to investigate a practical nonprobabilistic reliability assessment method on key strata. The mechanical tests and the hollow inclusion triaxial strain tests were conducted to measure relevant mechanical parameters and in situ stress. Furthermore, against the typical failure features in Datong Diggings, China, a shear failure mechanical model of key strata is proposed. Then, an allowable-safety-factor based nonprobabilistic stability probability assessment method is given. The sensitivity of geometrical dimensions and uncertainty levels of friction angle and cohesion are further studied. It is found that thickness and span of key strata have more dominative effect on key strata’s stability compared with the other factor and the increase of uncertainty levels results in decrease of stability probability.

Sign in / Sign up

Export Citation Format

Share Document